A child's primary teeth are an essential part of the body in terms of growth and development. The primary teeth are present in the mouth from 6 months old until around 12 years old. An intact dentition during this time of active growth is essential for proper nutritional intake. Digestion and assimilation of food requires the breakdown that only chewing can provide.
The primary teeth and the chewing process help stimulate the growth of the upper and lower jaw. They are also essential in the development of sound production and speech.
Primary teeth also retain space in the dental arch for their permanent teeth. When the primary teeth are prematurely lost, the permanent teeth are more often impacted or erupted in lingual and buccal version.

The primary teeth serve an esthetics function in children. There may be concerns with a positive self image when teeth are not present that should be, and when teeth are not lost on the same schedule as other children. Differences in what is considered "normal" appearance can be a source of teasing.
If a child has a lot of cavities, instead of just ripping the teeth out, the teeth should be restored such that all of the functions stated above can be adequately met.